This report describes a study of ramp signing for trucks. The research addressed methods for treating interchange ramps that are prone to cause high center of gravity vehicles to lose control and overturn. A critical review of the pertinent literature on interchange ramp design, signing, and overturning truck accidents was conducted. A state-of-the-practice review was also conducted in 12 States. This review determined the nature and extent of the truck rollover accident problem, determined problem ramp identification procedures, and identified active and passive treatments currently being used at problem ramps. A 'design-a-sign' study was conducted using 61 professional truck drivers. This study attempted to identify critical ramp cheracteristics and to develop innovative procedures for effectively communicating this information to approaching drivers. A series of laboratory studies were conducted to identify the specific sign elements and the specific sign format that most effectively warn truck drivers about potentially dangerous ramps. Two of the lab studies, using 117 trucker subjects, determined which sign elements, either words or symbols, were most effective. A third lab study, involving 44 truckers, determined the most effective format of the various sign elements. A fourth lab study, using 60 truckers and 27 non-truckers, involved meaning And preference testing of the most promising sign formats. The final laboratory procedure examined the relative visibility of the final sign formats. Seventy-two truckers were tested in that procedure. A field test was conducted at two interchange ramps in Virginia and Maryland that had high incidences of truck rollover accidents. A truck tipping sign with activated flashing beacons was installed at the ramp and an advance warning sign was installed prior to the ramp. Control sites received no treatment. Analysis indicated that the speeds of tractor trailers, in general, and top-heavy tractor trailers, in particular, were not affected by the experimental treatments. Speeds of automobiles showed a small but statistically significant speed reduction. The project concludes that truckers have a relatively high level of understanding regarding the truck rollover problem and the meaning of the truck tipping sign. Unfortunately, the field test results failed to show an operational effect to support this cognitive awareness. Nevertheless, the high level of understanding associated with the signs suggests that their use at high accident locations may be appropriate. (Author/publisher)
Abstract